“Please sign the petition appealing to Her Majesty The Queen to honour Astronaut Chris Hadfield — a true Canadian and Commonwealth icon — with a substantive knighthood for his extraordinary achievement in galvanizing worldwide interest in space exploration.http://www.gopetition.com/petitions/make-astronaut-chris-hadfield-a-knight.html
A former Royal Canadian Air Force pilot, Colonel Chris Hadfield was the first Canadian to walk in space. Hadfield has flown two space shuttle missions and served as commander of the International Space Station.
During the mission as commander of Expedition 35 he gained immense popularity by chronicling life aboard the space station and taking pictures of the earth and posting them through Twitter and Facebook to a large following of people around the world. From his perch in orbit, he was a guest on television news and talk shows and gained immense popularity by playing his guitar in space. His rendition of David Bowie’s “Space Oddity” is easily considered to be “one of the best videos of all time,” viewed by more than 16 million people around the globe.

As the first Commonwealth citizen to command the ISS, Astronaut Chris Hadfield inspired people the world over, especially the next-generation of scientists and engineers, and once again brought international popular attention to space expeditions — all while running the most productive science mission to date. His exceptional achievements in space have made him, in the words of one BBC commentator, “the most famous astronaut since the days of Neil Armstrong and Yuri Gagarin.”
Given these outstanding contributions, we the undersigned believe a knighthood as something personal from the Queen, over and above any Canadian honours, would be highly appropriate to reflect the pride and gratitude of the whole Commonwealth family.”

Personally I have always been in favour of knighthoods and have always been eager to debate the merits and legitimacy of the Nickle Resolution. Certainly Chris Hadfield seems quite deserving of such an honour to me. Although whether an online petition is truly the best way to lobby the government for a change in honours policy is something I am rather less confident of.
EDIT: The petitioner has decided that petitions are not the appropriate method for petitioning for royal honours, for they “are nominated discretely, not campaigned for in the open.” I would agree with that.